U.S. Pat. No. 3,309,089 to R. V. Doyle discloses a golfer's aid which may be used as a plumb bob by the golfer to help a golfer determine the contour of a putting green. The aid includes a pocket-watch shaped case, a spring loaded winding drum mounted inside the case, a nylon plumb line attached at one end thereof to the winding drum and a knurled knob which is screwed into the case and attached to the other end of the plumb line.
To determine the contour of a putting green with Doyle's aid, one must first unscrew the knob from the case and then pull on the knob to unwind the plumb line from the winding drum. The knob is then held in one hand and the case is allowed to freely dangle from the knob. As such, the case serves as a plumb bob to find true verticality, thereby helping the golfer determine the contour of the green.
Other patents disclosing plumb bob apparatus include U.S. Pat. Nos. 3,242,582 and 2,136,072.
While Doyle's aid undoubtedly works as intended, it is somewhat difficult to use in that the knob must first be unscrewed from the case and then pulled out of the case to unwind the plumb line. In addition, after using the aid to determine the contour of a putting green, the knob of Doyle's aid must be screwed back into the case. Accordingly, it would be desirable if a device for helping a golfer determine the contour of a putting green were available that is easier to use than that disclosed in Doyle. It would also be desirable if such an aid were inexpensive and easy to assemble.